Image display device

ABSTRACT

The image display device further includes a scanning unit that uses light from the light source to scan the movable screen and the fixed screen, and an optical system that uses light from the movable screen and the fixed screen to generate a virtual image, a drive unit that moves the movable screen, a structure body that supports the fixed screen at a fixed position such that the fixed screen is closer to the optical system than the movable screen is, and a magnetic cover that covers a movable part of the drive unit. The structure body covers an area around an opening of the magnetic cover to shield the movable part of the drive unit from stray light travelling backward via the optical system.

BACKGROUND 1. Technical Field

The present disclosure relates to an image display device. For example,the present disclosure relates to an image display device suitable forbeing mounted on a moving body such as a passenger vehicle.

2. Description of the Related Art

In recent years, an image display device called a head-up display hasbeen developed, and the head-up display has been mounted on a movingbody such as a passenger vehicle. In the head-up display mounted on thepassenger vehicle, light modulated based on image information isprojected toward a windshield, and the light reflected by the windshieldis applied to driver's eyes. This enables the driver to view a virtualimage of an image in front of the windshield. For example, a vehiclespeed or an outside air temperature is displayed as the virtual image.Recently, it is also considered to display, as a virtual image, anavigation image and an image for calling the attention on thepassengers to the driver.

In the head-up display, a laser light source such as a semiconductorlaser can be used as a light source to generate a virtual image. Thisconfiguration causes a screen to be scanned with laser light modulatedbased on a video signal. The screen diffuses the laser light to widen arange in which the laser light is applied to driver's eyes. Thisconfiguration prevents the driver's eyes from getting out of theirradiated region even if the driver moves his or her head to someextent, which allows the driver to view the image (virtual image)satisfactorily and stably.

PTL 1 discloses a configuration in which a screen is moved in an opticalaxis direction to vary an image-forming position of a virtual image in afront-back direction. In this configuration, a motor, a feed screw, anda rack are used for driving the screen.

CITATION LIST Patent Literature

PTL 1: Unexamined Japanese Patent Publication No. 2009-150947

SUMMARY

A series of images are rendered on a screen that is being moved in anoptical axis direction at a high speed. This enables display of an imagewhose visual distance varies in a depth direction (hereafter, referredto as a “depth image”). With this configuration, a depth image such asan arrow indicating a traveling direction of a vehicle can be displayedwhile being superimposed on a road at an intersection, for example.

Furthermore, an image is rendered on the screen that has been fixed.This enables display of an image whose visual distance is constant(hereafter, referred to as a “fixed image”) at a position with apredetermined visual distance as a virtual image. With thisconfiguration, information such as a vehicle speed or an outside airtemperature can be displayed. In this case, a visual distance of thefixed image is set remarkably shorter than a visual distance of thedepth image. For example, the visual distance of the depth image is setto about 10 m to about 100 m, and the visual distance of the fixed imageis set to about 3 m. As described above, in a case where a range of thevisual distance largely varies, when one screen is caused to displayboth the depth image and the fixed image, a movement range of the screenis remarkably extended. This makes it difficult to stably move thescreen at a high speed.

This may further cause stray light such as natural light travelingbackward via a projection optical system to enter the screen. In thiscase, the stray light is condensed to an area around the screen by theprojection optical system, which results in the area around the screenbeing irradiated with the stray light of high intensity. This may causea member located around the screen to be heated to a high temperature.Thus, it is required that the member located around the screen beprotected from such stray light.

In light of the foregoing, an object of the present disclosure is toprovide an image display device capable of moving a screen forgenerating a depth image smoothly at a high speed and suitablyprotecting a movable part located around the screen from stray light.

An image display device according to a primary aspect of the presentdisclosure includes a light source, a movable screen, a fixed screen, ascanning unit, an optical system, a drive unit, a fixed support part,and a cover. The movable screen is irradiated with light from the lightsource to form an image. The fixed screen is irradiated with the lightfrom the light source to form an image. The scanning unit uses the lightfrom the light source to scan the movable screen and the fixed screen.The optical system uses light from the movable screen and the fixedscreen to generate a virtual image. The drive unit moves the movablescreen in an incident direction of the light. The fixed support partsupports the fixed screen at a fixed position such that the fixed screenis closer to the optical system than the movable screen is. The covercovers the drive unit. Herein, the cover has an opening that guideslight from the scanning unit to the movable screen and the fixed screen.The drive unit supports the movable screen so as to allow the movablescreen to protrude toward the optical system through the opening. Thefixed support part covers an area around the opening to shield a movablepart of the drive unit from stray light travelling backward via theoptical system

The image display device according to the present aspect is configuredto move only the movable screen, which allows the movable screen to bemoved only within a range necessary for a depth image to be displayed.Accordingly, the movable screen can be moved smoothly at a high speed.Furthermore, the fixed support part that supports the fixed screencovers the area around the opening of the cover to shield the movablepart from the stray light travelling backward via the optical system,which makes it possible to prevent the area around the movable screenfrom being irradiated with the stray light of high intensity and thenprevent the movable part located around the movable screen from beingheated to a high temperature by the stray light. Accordingly, themovable part located around the movable screen can be suitably protectedfrom the stray light.

Thus, the image display device according to the present aspect iscapable of moving a screen for generating a depth image smoothly at ahigh speed and suitably protecting a movable part located around thescreen from stray light.

As described above, the present disclosure can provide an image displaydevice capable of moving a screen for generating a depth image smoothlyat a high speed and suitably protecting a movable part located aroundthe screen from stray light.

Effects or meanings of the present disclosed technology will be furtherclarified in the following description of the exemplary embodiment.However, the exemplary embodiment described below is merely an exampleof implementing the present disclosure, and the present disclosure isnot at all limited to the examples described in the following exemplaryembodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagram schematically illustrating a usage form of an imagedisplay device according to an exemplary embodiment;

FIG. 1B is a diagram schematically illustrating the usage form of theimage display device according to the exemplary embodiment;

FIG. 1C is a diagram schematically illustrating a configuration of theimage display device according to the exemplary embodiment;

FIG. 2 is a block diagram of an irradiation light generator and circuitsused in the irradiation light generator of the image display deviceaccording to the exemplary embodiment;

FIG. 3A is a perspective view schematically illustrating a configurationof a screen according to the exemplary embodiment;

FIG. 3B is a diagram schematically illustrating a scanning method of alaser beam with respect to the screen according to the exemplaryembodiment;

FIG. 4A is a perspective view illustrating a configuration of a driveunit according to the exemplary embodiment, with a structure body thatsupports a fixed screen installed on the drive unit;

FIG. 4B is a perspective view illustrating the configuration of thedrive unit according to the exemplary embodiment;

FIG. 5A is a perspective view illustrating the configuration of thedrive unit according to the exemplary embodiment, with a structure bodythat supports a movable screen, the structure body that supports thefixed screen, and a magnetic cover removed from the drive unit;

FIG. 5B is a perspective view illustrating a configuration of a supportbase according to the exemplary embodiment;

FIG. 6A is a perspective view illustrating a configuration of a magneticcircuit according to the exemplary embodiment;

FIG. GB is a perspective view illustrating the configuration of themagnetic circuit according to the exemplary embodiment;

FIG. 7 is an exploded perspective view illustrating an assembly step ofthe support base and a fixing base according to the exemplaryembodiment;

FIG. 8A is a perspective view illustrating a configuration of a supportmember and suspensions according to the exemplary embodiment, with thesupport member and the suspensions assembled;

FIG. 8B is a plan view illustrating a configuration of one of thesuspensions according to the exemplary embodiment;

FIG. 8C is a plan view illustrating a configuration of the othersuspension according to the exemplary embodiment;

FIG. 9A is an exploded perspective view illustrating an attachmentstructure of one of the suspensions to the support member according tothe exemplary embodiment;

FIG. 9B is an exploded perspective view illustrating the attachmentstructure of one of the suspensions to the support member according tothe exemplary embodiment;

FIG. 10A is an exploded perspective view illustrating a configuration ofthe structure body that supports the movable screen according to theexemplary embodiment;

FIG. 10B is a perspective view of an assembled body illustrating theconfiguration of the structure body that supports the movable screenaccording to the exemplary embodiment;

FIG. 11A is an exploded perspective view illustrating a configuration ofthe structure body that supports the fixed screen according to theexemplary embodiment;

FIG. 11B is a perspective view of an assembled body illustrating theconfiguration of the structure body that supports the fixed screenaccording to the exemplary embodiment;

FIG. 12A is a plan view illustrating a configuration of a holder thatsupports the fixed screen according to the exemplary embodiment;

FIG. 12B is a plan view illustrating the configuration of the holderaccording to the exemplary embodiment, with the fixed screen installedon the holder;

FIG. 13A is a plan view illustrating a configuration around a peripheryof the magnetic cover according to the exemplary embodiment, before thestructure body that supports the fixed screen is installed on themagnetic cover;

FIG. 13B is a plan view illustrating the configuration around theperiphery of the magnetic cover according to the exemplary embodiment,with the structure body that supports the fixed screen installed on themagnetic cover;

FIG. 14A is a diagram schematically illustrating a positionalrelationship between the movable screen and the fixed screen accordingto the exemplary embodiment;

FIG. 14B is a diagram schematically illustrating a scanning method ofthe laser beam with respect to the movable screen and the fixed screenaccording to the exemplary embodiment;

FIG. 15A is a graph illustrating an example of driving the movablescreen according to the exemplary embodiment;

FIG. 15B is a diagram schematically illustrating an example of imagedisplay according to the exemplary embodiment; and

FIG. 16 is a cross-sectional view illustrating how stray light isincident according to the exemplary embodiment.

DETAILED DESCRIPTION

Hereinafter, an exemplary embodiment of the present disclosure will bedescribed with reference to the accompanying drawings. X, Y, and Z-axesperpendicular to one another are added to each of the drawings. Thepresent exemplary embodiment corresponds to an on-vehicle head-updisplay to which the present disclosure is applied.

Note that, in the following exemplary embodiment, structure body 302corresponds to a “fixed support part” described in the appended claims,magnetic cover 308 corresponds to a “cover” described in the appendedclaims, and structure body 301 and support member 303 each correspond toa “movable part” described in the appended claims. However, suchcorrespondences are not intended to impose limitations on significancesof the respective terms described in the appended claims.

FIG. 1A and FIG. 1B are diagrams each schematically illustrating a usageform of image display device 20. FIG. 1A is a diagram schematicallyillustrating, in a see-through manner, an inside of passenger vehicle 1as viewed from a side of passenger vehicle 1, and FIG. 1B is a view of afront of passenger vehicle 1 in a driving direction as seen from theinside of passenger vehicle 1.

As illustrated in FIG. 1A, image display device 20 is installed insidedashboard 11 of passenger vehicle 1.

As illustrated in FIG. 1A and FIG. 1B, image display device 20 projectslaser light, which is modulated based on a video signal, onto projectionregion 13 near a driver's seat on a lower side of windshield 12. Thelaser light is reflected by projection region 13, and is applied to anoblong region (eyebox region) around eyes of driver 2. This causespredetermined image 30 to be displayed as a virtual image in a viewingfield in front of driver 2. Therefore, driver 2 can view image 30, whichis the virtual image, superimposed on a scene in front of windshield 12.In other words, image display device 20 forms image 30, which is thevirtual image, in a space in front of projection region 13 of windshield12.

FIG. 1C is a diagram schematically illustrating a configuration of imagedisplay device 20.

Image display device 20 includes irradiation light generator 21 andmirror 22. Irradiation light generator 21 emits light modulated based onthe video signal. Mirror 22 has a curved reflecting surface andreflects, toward windshield 12, the light emitted from irradiation lightgenerator 21. The light reflected by windshield 12 is applied to eye 2 aof driver 2. An optical system of irradiation light generator 21 andmirror 22 are designed such that image 30 as the virtual image can bedisplayed in a predetermined size in front of windshield 12.

Mirror 22 constitutes an optical system that uses light from movablescreen 108 and fixed screen 109 (described later) to generate thevirtual image. This optical system does not necessarily have to beconstituted only of mirror 22. For example, this optical system mayinclude a plurality of mirrors, and may include a lens or othercomponents.

FIG. 2 is a diagram illustrating configurations of irradiation lightgenerator 21 of image display device 20 and of circuits used inirradiation light generator 21.

Irradiation light generator 21 includes light source 101, collimatorlenses 102 a to 102 c, mirror 103, dichroic mirrors 104, 105, scanningunit 106, correction lens 107, movable screen 108, fixed screen 109, anddrive unit 300.

Light source 101 includes three laser light sources 101 a to 101 c.Laser light sources 101 a to 101 c respectively emit laser light in ared wavelength band, laser light in a green wavelength band, and laserlight in a blue wavelength band. In the present exemplary embodiment, inorder to display a color image as image 30, light source 101 includesthree laser light sources 101 a to 101 c. In a case where a monochromeimage is displayed as image 30, light source 101 may include only onelaser light source corresponding to a color of the image. Laser lightsources 101 a to 101 c are, for example, semiconductor lasers.

Laser beams emitted from laser light sources 101 a to 101 c arerespectively converted into substantially parallel light by collimatorlenses 102 a to 102 c. At this time, the laser beam emitted from each oflaser light sources 101 a to 101 c is shaped into a circular beam shapeby an aperture (not illustrated). Note that, in place of collimatorlenses 102 a to 102 c, shaping lenses may be used, each of which shapesthe laser beam into a circular beam shape and collimates the laser beam.In such a case, the aperture can be omitted.

Then, with regard to the laser beams of the respective colors emittedfrom laser light sources 101 a to 101 c, their respective optical axesare aligned with one another by mirror 103 and two dichroic mirrors 104,105. Mirror 103 substantially totally reflects the red laser beamtransmitted through collimator lens 102 a. Dichroic mirror 104 reflectsthe green laser beam transmitted through collimator lens 102 b, andtransmits the red laser beam reflected by mirror 103. Dichroic mirror105 reflects the blue laser beam transmitted through collimator lens 102c, and transmits the red laser beam that has passed through dichroicmirror 104 and the green laser beam that has reflected by dichroicmirror 104. Mirror 103 and two dichroic mirrors 104, 105 are disposed soas to align the optical axes of the laser beams of the respective colorswith one another, the laser beams being emitted from laser light sources101 a to 101 c.

Scanning unit 106 reflects the laser beams of the respective colors thathave passed through or reflected by dichroic mirror 105. Scanning unit106 is comprised of, for example, a micro electro mechanical system(MEMS) mirror and is configured to rotate mirror 106 a, onto which thelaser beams of the respective colors having passed through dichroicmirror 105 are made incident, about an axis parallel to the Y-axis andan axis perpendicular to the Y-axis in response to a drive signal. Therotation of mirror 106 a changes a reflection direction of the laserbeam in an in-plane direction of an X-Z plane and in an in-planedirection of a Y-Z plane. In this way, as will be described later,movable screen 108 and fixed screen 109 are scanned with the laser beamsof the respective colors.

Note that, although scanning unit 106 is comprised of such a two-axisdriving MEMS mirror herein, scanning unit 106 may have anotherconfiguration. For example, scanning unit 106 may be comprised of acombination of a mirror that is rotationally driven about the axisparallel to the Y-axis and a mirror that is rotationally driven aboutthe axis perpendicular to the Y-axis.

Correction lens 107 is designed to direct the laser beams of therespective colors in a positive direction of the Z-axis regardless of aswing angle of the laser beams deflected by scanning unit 106. Movablescreen 108 and fixed screen 109 are scanned with the laser beams to forman image, and diffuses the incident laser beams to a region (eyeboxregion) around eye 2 a of driver 2. Movable screen 108 and fixed screen109 are each made of a transparent resin such as polyethyleneterephthalate (PET).

Movable screen 108 is used to display a depth image whose visualdistance varies in a depth direction, and fixed screen 109 is used todisplay a fixed image whose visual distance is constant. For example, anarrow for guiding a vehicle in a traveling direction is displayed as thedepth image, and characters indicating a vehicle speed or an outside airtemperature are displayed as the fixed image.

Drive unit 300 drives movable screen 108 to reciprocate in a direction(Z-axis direction) parallel to a traveling direction of the laser beams.A configuration of drive unit 300 will be described later with referenceto FIG. 4A to FIG. 13B.

Image processing circuit 201 includes an arithmetic processing unit suchas a central processing unit (CPU) and a memory. Image processingcircuit 201 processes a video signal, which is input thereto, andcontrols laser drive circuit 202, mirror drive circuit 203, and screendrive circuit 204. Laser drive circuit 202 changes emission intensity oflaser light sources 101 a to 101 c in response to a control signal fromimage processing circuit 201. Mirror drive circuit 203 drives mirror 106a of scanning unit 106 in response to a control signal from imageprocessing circuit 201. Screen drive circuit 204 drives movable screen108 in response to a control signal from image processing circuit 201.Control in image processing circuit 201 during an image displayoperation will be described later with reference to FIG. 14A.

FIG. 3A is a perspective view schematically illustrating a configurationof movable screen 108. FIG. 3B is a diagram schematically illustrating ascanning method of laser beam with respect to movable screen 108.

As illustrated in FIG. 3A, a plurality of first lens portions 108 a fordiverging laser light in the X-axis direction are formed on a laser beamincident surface of movable screen 108 (that is, a surface on a negativeside of the Z-axis) so as to be arrayed in the X-axis direction. A shapeof each of first lens portions 108 a as viewed in the Y-axis directionis a substantially circular arc shape. A width in the X-axis directionof each of first lens portions 108 a is, for example, 50 μm.

Furthermore, a plurality of second lens portions 108 b for diverging thelaser beam in the Y-axis direction are formed on a laser beam emissionsurface of movable screen 108 (that is, a surface on a positive side ofthe Z-axis) so as to be arrayed in the Y-axis direction. A shape of eachof second lens portions 108 b as viewed in the X-axis direction is asubstantially circular arc shape. A width in the Y-axis direction ofeach of second lens portions 108 b is, for example, 70 μm.

The light incident surface (the surface on the negative side of theZ-axis) of movable screen 108 having the above-described configurationis scanned, as illustrated in FIG. 3B, in the positive direction of theX-axis with beam B1 composed of the laser beams of the respective colorsthat have been superimposed on one another. On the light incidentsurface of movable screen 108, scan lines L1 to Lk through which beam B1passes are set beforehand at constant intervals in the Y-axis direction.Start positions of scan lines L1 to Lk coincide with one another in theX-axis direction, and end positions of scan lines L1 to Lk coincide withone another in the X-axis direction. A diameter of beam B1 is set toapproximately 50 μm, for example.

Scan lines L1 to Lk are scanned by high frequency beam B1 composed ofthe laser beams of the respective colors that have been modulated basedon the video signal, thereby forming an image. The image thus formed isprojected onto the region (eyebox region) around eye 2 a of driver 2 viamovable screen 108, mirror 22, and windshield 12 (refer to FIG. 1C).This allows driver 2 to visually recognize image 30 as a virtual imagein a space in front of windshield 12.

Fixed screen 109 has a configuration similar to that of movable screen108. Fixed screen 109 is smaller in width than movable screen 108 in theY-axis direction. Fixed screen 109 is scanned with beam B1 in the X-axisdirection, similar to movable screen 108. A number of scan lines onfixed screen 109 is smaller than a number of scan lines on movablescreen 108.

In the present exemplary embodiment, only movable screen 108 is drivenby drive unit 300, and fixed screen 109 is fixed at a predeterminedposition. In order to display the depth image, movable screen 108 isscanned with beam B1 while being moved in an optical axis direction(Z-axis direction). In order to display the fixed image, fixed screen109 fixed at the predetermined position is scanned with beam B1.

Next, a configuration of drive unit 300 will be described.

FIG. 4A is a perspective view illustrating the configuration of driveunit 300 with structure body 302 that supports fixed screen 109installed thereon, and FIG. 4B is a perspective view illustrating theconfiguration of drive unit 300. FIG. 5A is a perspective viewillustrating the configuration of drive unit 300 with magnetic cover 308and structure body 301 that supports movable screen 108 removedtherefrom. Note that FIG. 4A, FIG. 4B, and FIG. 5A illustrate drive unit300 supported by support base 306 and fixing base 310.

Note that in the following, the configuration will be described,defining directions by X, Y, and Z-axes, and in addition, assuming thata side closer to a center of drive unit 300 and a side farther from thecenter of drive unit 300 in a plan view are respectively referred to asan inner side and an outer side, for the sake of convenience.

In FIG. 4A and FIG. 4B, movable screen 108 and fixed screen 109 areinstalled on structure body 301 and structure body 302, respectively, soas to be sloped in the same direction. Movable screen 108 and fixedscreen 109 are installed at positions that are aligned in a direction(Y-axis direction) perpendicular to a movement direction (Z-axisdirection) in which movable screen 108 is moved by drive unit 300 andthat are shifted from each other by a predetermined distance in themovement direction (Z-axis direction). Structure body 302 is installedon an upper surface of magnetic cover 308 to cover an area aroundopening 308 a of magnetic cover 308.

As illustrated in FIG. 4B, gap G1 is formed adjacent to movable screen108 on a positive side of the Y-axis. Fixed screen 109 is positioneddirectly above gap G1. Fixed screen 109 is scanned with the laser beampassing through gap G1.

Structure body 301 having movable screen 108 installed thereon isinstalled on inner frame 303 a of support member 303 illustrated in FIG.5A. Support member 303 is supported by two support units 305 that arealigned in the Y-axis direction so as to be movable in the Z-axisdirection via four suspensions 304. Support units 305 are installed onsupport base 306. Each of support units 305 includes gel covers 305 a onthe positive side and the negative side of the X-axis, and gel covers305 a are filled with gel for damping.

In this way, movable screen 108 is supported, movably in the Z-axisdirection, by support base 306 via structure body 301, support member303, suspensions 304, and support units 305. Configurations of supportmember 303 and suspensions 304 will be described later with reference toFIG. 8A to FIG. 8C. Furthermore, a configuration of support base 306will be described later with reference to FIG. 5B.

On support base 306, magnetic circuit 307 is further installed. Magneticcircuit 307 is configured to apply a magnetic field to coil 341 (referto FIG. 8A) mounted on support member 303. When a drive signal (current)is applied to coil 341, electromagnetic force in the Z-axis direction isgenerated in coil 341. The electromagnetic force thus generated drivessupport member 303 together with coil 341 in the Z-axis direction. Thiscauses movable screen 108 to move in the Z-axis direction. Aconfiguration of magnetic circuit 307 will be described later withreference to FIG. 6A and FIG. 6B.

Magnetic cover 308 is put on an upper surface of magnetic circuit 307.Magnetic cover 308 is made of a magnetic material and functions as ayoke of magnetic circuit 307. When magnetic cover 308 is put on theupper surface of magnetic circuit 307, magnetic cover 308 is attractedto magnetic circuit 307. Magnetic cover 308 is thus installed on driveunit 300.

As illustrated in FIG. 4B, magnetic cover 308 is provided with opening308 a through which structure body 301 passes. Furthermore, cutouts 308b are formed extending outward from opening 308 a. Cutouts 308 b areconfigured to allow beam 303 c (refer to FIG. 8A) of support member 303(described later) to pass therethrough. Magnetic cover 308 is furtherprovided with two threaded holes 308 c used for fastening structure body302 to magnetic cover 308 with screws and two holes 308 d used forpositioning structure body 302.

Support base 306 is installed on fixing base 310 via damper units 309.Damper units 309 support support base 306 while keeping support base 306in suspension in the positive direction of the Z-axis with respect tofixed base 310. Damper units 309 absorb vibration generated inassociation with the driving of support member 303 before the vibrationis transmitted from support base 306 to fixing base 310. Configurationsof damper units 309 and fixing base 310 will be described later withreference to FIG. 7.

On fixing base 310, position detection unit 400 is further installed.Position detection unit 400 includes printed circuit board 401 facing aside surface of support member 303 on the positive side of the X-axis.An encoder (not illustrated) is disposed on a surface of printed circuitboard 401 on the negative side of the X-axis. This encoder detects aposition of support member 303 in the Z-axis direction. A method fordetecting the position of support member 303 with the encoder will bedescribed later with reference to FIG. 8A.

FIG. 5B is a perspective view illustrating a configuration of supportbase 306 as viewed from the positive side of the Z-axis.

As illustrated in FIG. 5B, support base 306 has an approximatelyrectangular shape in a plan view. Support base 306 is made of a highlyrigid metal material. At a center of support base 306, opening 311 isformed to allow laser light to pass therethrough. Furthermore, at eachof four corners of support base 306, circular hole 313 is formed forinstalling each of damper units 309.

Moreover, at a central position in the X-axis direction in each of endsof support base 306 on the positive side and a negative side of theY-axis, opening 312 is formed for installing each of support units 305.In addition, on an upper surface (a surface on the positive side of theZ-axis) of support base 306, a plurality of bosses 314 for positioningmagnetic circuit 307 and support units 305 are formed.

FIG. 6A and FIG. 6B are perspective views each illustrating aconfiguration of magnetic circuit 307.

Magnetic circuit 307 includes two yokes 321 aligned in the Y-axisdirection. Yokes 321 have a U-shape as viewed in the X-axis direction.Each of two yokes 321 has two separated inner walls 321 b. On an innerside of outer wall 321 a of each of yokes 321, magnet 322 is installed.Furthermore, on an outer side of each of two walls 321 b located on aninner side of each of yokes 321, magnet 323 is installed so as to facemagnet 322. Between magnet 322 and magnets 323 facing each other, a gapis formed into which coil 341 (refer to FIG. 8A) to be described lateris inserted.

Magnetic circuit 307 further includes two yokes 324 aligned in theX-axis direction. Yokes 324 have a U-shape as viewed in the Y-axisdirection. Each of two yokes 324 has two separated outer walls 324 a andtwo separated inner walls 324 b. On an inner side of each of two walls324 a located on an outer side of each of yokes 324, magnet 325 isinstalled. Furthermore, on an outer side of each of two walls 324 blocated on an inner side of each of yokes 324, magnet 326 is installedso as to face corresponding magnet 325. Between magnets 325 and magnets326 facing each other, a gap is formed into which coil 341 (refer toFIG. 8A) to be described later is inserted. An end of each of magnets326 in the Y-axis direction overlaps a side surface of inner wall 321 bof adjacent yoke 321.

In each of lower surfaces of two yokes 321 and each of lower surfaces oftwo yokes 324, holes (not illustrated) are formed at positions intowhich bosses 314 of support base 306 illustrated in FIG. 5B are fitted.Yokes 321, 324 are installed on an upper surface of support base 306such that bosses 314 are fitted into the holes formed in the lowersurfaces of yokes 321, 324. As illustrated in FIG. 6B, magnetic circuit307 is thus installed on the upper surface of support base 306.

FIG. 7 is an exploded perspective view illustrating an assembly step ofsupport base 306 and fixing base 310.

As illustrated in FIG. 7, each of damper units 309 includes damper 309a, washer 309 b, and screw 309 c. Fixing base 310 includes: opening 331through which laser light passes; threaded holes 332 for receivingscrews 309 c; opening 333 for installing position detection unit 400;and bosses 334 for positioning position detection unit 400. Fixing base310 is integrally formed of a highly rigid metal material.

Dampers 309 a are each integrally formed of a material that has anexcellent damping property. Dampers 309 a are each formed of, forexample, a material with high viscous damping such as αGEL (registeredtrademark) or rubber. A sleeve of a cylindrical shape is fitted into ahole formed at a center of each of dampers 309 a. Each of dampers 309 ais fitted into hole 313 formed at each of four corners of support base306. In this state, washers 309 b are put on the upper surfaces ofdampers 309 a. Further, screws 309 c are inserted through washers 309 band screwed in threaded holes 332 of fixing base 310. This causessupport base 306 to be supported by fixing base 310 via dampers 309 a.

FIG. 8A is a perspective view illustrating a configuration of supportmember 303 and suspensions 304 with support member 303 and suspensions304 assembled.

As illustrated in FIG. 8A, support member 303 has a frame shape. Supportmember 303 is formed of a lightweight and highly rigid material. In thepresent exemplary embodiment, support member 303 is formed of a liquidcrystal polymer in which a carbon filler is mixed. Support member 303includes inner frame 303 a and outer frame 303 b both having anapproximately rectangular shape in a plan view. Inner frame 303 a andouter frame 303 b are connected to each other with four beams 303 c suchthat a center of inner frame 303 a and a center of outer frame 303 bcoincide with each other in a plan view. Inner frame 303 a is in aposition shifted upward (the positive direction of the Z-axis) fromouter frame 303 b.

Structure body 301 is installed on an upper surface of inner frame 303a. Furthermore, coil 341 is mounted on a lower surface of outer frame303 b. Coil 341 extends along the lower surface of outer frame 303 b soas to have a rectangular shape with round corners.

At each of four corners of outer frame 303 b, connection part 303 d isformed extending radially. Each of connection parts 303 d has an upperflange and a lower flange. To an upper surface of the upper flange ofeach of connection parts 303 d, an end of upper suspension 304 is fixedwith fixing member 303 e. Furthermore, to a lower surface of the lowerflange of each of connection parts 303 d, an end of lower suspension 304is fixed with fixing member 303 e. This causes suspensions 304 to bemounted on support member 303.

Support member 303 further includes bridges 303 f each connectingconnection parts 303 d that are neighboring to each other in the Y-axisdirection. A part of each bridge 303 f except both ends in the Y-axisdirection extends parallel to the Y-axis direction, and at a center ofthe part, installing surface 303 g parallel to a Y-Z plane is provided.A scale is installed on installing surface 303 g of bridge 303 f, on thepositive side of the X-axis, of support member 303.

Two suspensions 304 on the positive side of the Y-axis and twosuspensions 304 on the negative side of the Y-axis are mounted tosupport units 305 as illustrated in FIG. 5A. This causes coil 341mounted on the lower surface of outer frame 303 b to be inserted intothe gap between the mutually facing magnets of magnetic circuit 307illustrated in FIG. 6B. Furthermore, the scale installed on installingsurface 303 g of bridge 303 f, on the positive side of the X-axis, ofsupport member 303 faces the encoder installed on printed circuit board401 of position detection unit 400.

The encoder of position detection unit 400 includes an optical sensorthat emits light to the scale and receives light reflected from thescale, and the optical sensor optically detects movement of the scale inthe Z-axis direction. On the basis of a detection signal from theencoder, a position of support member 303 and movable screen 108 in theZ-axis direction is detected. On the basis of the detected position,driving of movable screen 108 is controlled.

Note that magnetic poles of magnets 322, 323, 325, 326 of magneticcircuit 307 illustrated in FIG. 6A and FIG. 6B are adjusted such that adrive signal (current) applied to coil 341 causes coil 341 to generatedriving force in one direction parallel to the Z-axis direction.

FIG. 8B and FIG. 8C are plan views each illustrating a configuration ofeach of suspensions 304.

In the present exemplary embodiment, a shape of suspension 304 on anupper side (the positive side of the Z-axis) and a shape of suspension304 on a lower side (the negative side of the Z-axis) illustrated inFIG. 8A are different from each other. Herein, suspension 304 on theupper side is referred to as suspension 304-1, and suspension 304 on thelower side is referred to as suspension 304-2, for the sake ofconvenience.

Suspensions 304-1, 304-2 are thin plate-shaped members and are eachintegrally formed of a conductive and flexible metal material.Suspensions 304-1, 304-2 are made of a beryllium copper alloy, forexample. Suspensions 304-1, 304-2 each have a symmetrical shape withrespect to a central position in the X-axis direction. Suspensions304-1, 304-2 each have three holes 304 a, at the central position in theX-axis direction, used for mounting suspension 304-1, 304-2 on supportunit 305. Furthermore, suspensions 304-1, 304-2 each have flexiblestructures 304 b of a crank shape on both sides of three holes 304 a.

Moreover, suspensions 304-1, 304-2 each have a pair of flanges 304 cprotruding in the positive direction of the Y-axis. Furthermore,suspensions 304-1, 304-2 each have a pair of arms 304 d extending in theX-axis direction, and have hole 304 e at an end of each of arms 304 d.Moreover, suspensions 304-1, 304-2 each have a pair of flanges 304 fprotruding from the respective ends of arms 304 d in the negativedirection of the Y-axis.

Moreover, suspensions 304-1, 304-2 each have a pair of hooks 304 g onrespective end sides of flexible structures 304 b. When movable screen108 is reciprocated in the Z-axis direction, suspensions 304-1, 304-2are deformed into an S-shape in the Z-axis direction. Hooks 304 g aredisposed in each of suspensions 304-1, 304-2 so as to be positioned atrespective inflection points of the deformations. As illustrated in FIG.4A, hooks 304 g are housed in gel covers 305 a. Hooks 304 g are providedto enhance a damping effect caused by the gel.

Respective flexible structures 304 b of suspensions 304-1, 304-2 aredifferent in shape from each other. Specifically, each of flexiblestructures 304 b of suspension 304-1 is formed by providing cutouts C1and C2 extending from the negative and positive sides of the Y-axis,respectively. In contrast, each of flexible structures 304 b ofsuspension 304-2 is formed only by providing cutout C3 extending fromthe negative side of the Y-axis. Structures of suspensions 304-1, 304-2other than the shapes of flexible structures 304 b are identical to eachother.

Providing flexible structures 304 b allows suspensions 304-1, 304-2 toeasily deform in the Z-axis direction. This configuration allows supportmember 303 supporting structure body 301 and movable screen 108 to moveat a high speed in the Z-axis direction.

Furthermore, flexible structure 304 b of upper suspension 304-1 isdifferent from flexible structure 304 b of lower suspension 304-2, whichallows buckling rigidity of suspension 304-1 to differ from bucklingrigidity of suspension 304-2. The buckling rigidity herein indicates adegree of difficulty in deformation of suspensions 304-1, 304-2 againstexternal force (compression or tension) in the positive or negativedirection of the X-axis, and can be represented by (load/deformationquantity).

The buckling rigidity of upper suspension 304-1 is made different fromthe buckling rigidity of lower suspension 304-2 in this manner.Therefore, when support member 303 supporting structure body 301 andmovable screen 108 is reciprocated at a high frequency in the Z-axisdirection, generation of excessive amplitude owing to a resonance modecan be suppressed.

Note that, in the present exemplary embodiment, suspensions 304-1, 304-2double as a feeding path of the drive signal to coil 341. In the presentexemplary embodiment, as described above, support member 303 is formedof a liquid crystal polymer in which a carbon filler is mixed, whichmakes support member 303 conductive. Accordingly, the configuration inwhich suspensions 304-1, 304-2 double as a feeding path requires that anattachment structure of suspensions 304-1, 304-2 to support member 303be electrically insulated.

FIG. 9A and FIG. 9B are exploded perspective views each illustrating theattachment structure of suspension 304-1 to support member 303.

As illustrated in FIG. 9A, fixing member 303 e includes screw 351 andtwo plate-shaped clampers 352. Upper and lower surfaces of each of twoclampers 352 are subjected to an oxidation treatment to be electricallyinsulated. Furthermore, a hole is provided at a center of each ofclampers 352. A shaft of screw 351 is smaller in diameter than the holeof clamper 352 and hole 304 e of suspension 304-1. Furthermore, hole 304e of suspension 304-1 is made larger in diameter than the hole ofclamper 352, which prevents screw 351 from coming into contact withsuspension 304-1.

With hole 304 e of suspension 304-1 and the respective holes of twoclampers 352 aligned with each other, each end of suspension 304-1 isinterposed between two clampers 352. In this state, the ends ofsuspension 304-1 are placed on upper surfaces of connection parts 303 dof support member 303, and screws 351 are screwed into threaded holes303 h of connection parts 303 d. This causes the ends of suspension304-1 to be fixed to the upper surfaces of connection parts 303 d ofsupport member 303, as illustrated in FIG. 9B. Similarly, lowersuspension 304-2 is also fixed to lower surfaces of connection parts 303d.

The upper and lower surfaces of each of two clampers 352 areelectrically insulated; thus, even when the ends of suspensions 304-1,304-2 are screwed in this manner, suspensions 304-1, 304-2 are notelectrically connected with support member 303. This configurationallows suspensions 304-1, 304-2 to be appropriately used as the feedingpath to coil 341.

After suspensions 304-1, 304-2 are thus mounted on support member 303,an end of coil 341 (refer to FIG. 8A) mounted on outer frame 303 b ofsupport member 303 is connected, by soldering, to flanges 304 f formedon the ends of suspension 304-1 or suspension 304-2. Furthermore, a leadwire for supplying the drive signal to coil 341 is connected, bysoldering, to flanges 304 c of suspension 304-1 or suspension 304-2. Thedrive signal is thus supplied to coil 341 through suspension 304-1 orsuspension 304-2.

Next, a configuration of structure body 301 that supports movable screen108 will be described.

FIG. 10A is an exploded perspective view illustrating a configuration ofstructure body 301, and FIG. 10B is a perspective view of an assembledbody corresponding to structure body 301.

As illustrated in FIG. 10A, structure body 301 includes movable screen108, holder 361, a heat resistant member (hereinafter, referred to as a“heat resistant packing”) 362, and light shielding member 363.

Holder 361 is a frame-shaped member of which a top and a bottom areopened. Holder 361 is formed of a lightweight and highly rigid material.In the present exemplary embodiment, holder 361 is integrally molded ofa magnesium alloy. A shape of holder 361 is symmetry with respect to theX-axis direction.

Holder 361 has an approximately rectangular shape in a plan view. Aportion of holder 361 on the positive side of the Y-axis is lower thanthe other portions. Accordingly, an upper surface of holder 361 issloped in the Z-axis direction relative to a plane parallel to an X-Yplane. On the upper surface of holder 361, stepped part 361 a isprovided extending along a periphery of holder 361. A depth of steppedpart 361 a is approximately equal to a thickness of movable screen 108.On each of lower surfaces of holder 361 on the positive side and thenegative side of the Y-axis, two engagement parts 361 b are provided.Engagement parts 361 b are rectangular cutouts extending from the lowersurfaces in the positive direction of the Z-axis. On the lower surfaceof holder 361, a plurality of protrusions 361 c are provided extendingdownward from an inner side of the lower surface.

Heat resistant packing 362 is made of an elastically deformable materialthat has excellent heat resistance and heat insulation properties. Heatresistant packing 362 is formed of, for example, heat resistant siliconerubber. Heat resistant packing 362 is a frame-shaped member having asubstantially square cross-section. Heat resistant packing 362 is shapedto fit into stepped part 361 a of holder 361.

Light shielding member 363 is made of a thin plate-shaped member. Lightshielding member 363 has a thickness of about 0.2 mm, for example. Lightshielding member 363 is formed of a lightweight material that hasexcellent heat resistance and light shielding properties. Lightshielding member 363 is formed of a magnesium alloy, for example. Lightshielding member 363 has opening 363 a of a rectangular shape. Opening363 a is slightly smaller in size than heat resistant packing 362. Onedges of light shielding member 363 on the positive side and thenegative side of the Y-axis, hooks 363 b that each engage with acorresponding engagement part 361 b of holder 361 are provided.

Movable screen 108 is fitted into stepped part 361 a of holder 361 suchthat an end of movable screen 108 on the negative side of the Y-axiscomes into contact with an inner wall of stepped part 361 a on thenegative side of the Y-axis. Moreover, heat resistant packing 362 is puton an upper surface of movable screen 108 and stepped part 361 a so asto extend along stepped part 361 a. In this state, an upper surface ofheat resistant packing 362 protrudes beyond the upper surface of holder361 in the positive direction of the Z-axis. Then, light shieldingmember 363 is put over holder 361, and four hooks 363 b are engaged withfour respective engagement parts 361 b of holder 361. At this time, heatresistant packing 362 is compressed by light shielding member 363 in theZ-axis direction. Engagement of hooks 363 b with engagement parts 361 bis maintained by an elastic restoring force of heat resistant packing362.

As illustrated in FIG. 10B, assembly of structure body 301 is thuscompleted. In this state, rectangular gap G1 is present adjacent to aportion of movable screen 108 on the positive side of the Y-axis. Whenholder 361 is put on inner frame 303 a as illustrated in FIG. 4A,protrusions 361 c of holder 361 are fitted to an inner side of innerframe 303 a. Holder 361 is thus positioned on support member 303. Atthis time, the lower surface of holder 361 is bonded, with adhesive, tothe upper surface of inner frame 303 a. As a result, movable screen 108together with structure body 301 is installed on support member 303.

Next, structure body 302 that supports fixed screen 109 will bedescribed.

FIG. 11A is an exploded perspective view illustrating a configuration ofstructure body 302, and FIG. 11B is a perspective view of an assembledbody corresponding to structure body 302. FIG. 12A is a plan viewillustrating a configuration of holder 371, and FIG. 12B is a plan viewillustrating holder 371 and fixed screen 109 with fixed screen 109installed on holder 371.

Structure body 302 includes fixed screen 109, holder 371, lightshielding members 372, and screws 373, 374.

As illustrated in FIG. 11A and FIG. 12A, holder 371 is a frame-shapedmember. Holder 371 is formed of a lightweight material having a lightshielding property. For example, holder 371 is integrally formed byaluminum die-casting.

Holder 371 includes two recesses 371 a on which both ends of fixedscreen 109 are placed. A portion of each of recesses 371 a on thepositive side of the Y-axis is lower than the other portions.Accordingly, fixed screen 109 is installed on recesses 371 a so as to besloped in the Z-axis direction relative to the plane parallel to the X-Yplane. On a portion of holder 371 on the negative side of the Y-axis,stepped part 371 b is provided protruding in the positive direction ofthe Z-axis. Furthermore, opening 371 c is formed so as to partiallyoverlap stepped part 371 b. Opening 371 c has a rectangular shape in aplan view.

At an end of each of recesses 371 a on the negative side of the Y-axis,threaded hole 371 d is provided for receiving screw 373. An uppersurface of an area around threaded hole 371 d is flush with the uppersurface of holder 371 on the positive side of the Y-axis. On the uppersurface of holder 371 on the positive side of the Y-axis, two threadedholes 371 e are provided for receiving screws 373. At each of ends onthe upper surface of holder 371 on the positive side and the negativeside of the X-axis, recess 371 f is provided. Each of recesses 371 f hasa hole 371 g into which screw 374 is inserted.

Moreover, at each of ends of holder 371 on the positive side and thenegative side of the X-axis, leg 371 h is provided protruding downward.Therefore, holder 371 has an arch shape as viewed from the positive sideof the Y-axis. At an end on the positive side of the Y-axis on a lowersurface of leg 371 h on the positive side of the X-axis, protrusion 371i of a cylindrical shape is provided protruding downward. Furthermore,at an end on the negative side of the Y-axis on a lower surface of leg371 h on the negative side of the X-axis, protrusion 371 i of acylindrical shape (not illustrated) is provided protruding downward.

Light shielding members 372 are each made of a thin plate-shaped member.Light shielding members 372 have a thickness of about 0.2 mm, forexample. Light shielding members 372 are each formed of a lightweightmaterial that has excellent heat resistance and light shieldingproperties. Light shielding members 372 are each formed of a magnesiumalloy, for example. Light shielding members 372 each have holes 372 athrough which screws 373 pass.

Fixed screen 109 is placed on recesses 371 a of holder 371 such that anend of fixed screen 109 on the positive side of the Y-axis comes intocontact with an inner wall of holder 371 on the positive side of theY-axis. Then, fixed screen 109 is bonded, with adhesive, to bottomsurfaces of recesses 371 a. As illustrated in FIG. 12B, with fixedscreen 109 installed on recesses 371 a, both ends of fixed screen 109are spaced apart, in the positive direction of the Y-axis, from steppedportions in which threaded holes 371 d are formed. Furthermore, in thisstate, a portion of fixed screen 109 other than the ends is spaced apartfrom an inner wall of opening 371 c on the positive side of the Y-axis.That is, gap G2 is formed between fixed screen 109 and a portion ofholder 371 on the positive side of the Y-axis.

After fixed screen 109 is thus installed, two light shielding members372 are installed, with screws 373, on an upper surface of holder 371.This causes both the ends of fixed screen 109 to be covered by lightshielding members 372. As illustrated in FIG. 11B, assembly of structurebody 302 is thus completed.

Protrusions 371 i provided on the respective lower surfaces of two legs371 h are fitted into holes 308 d of magnetic cover 308 illustrated inFIG. 4B, which causes structure body 302 after the assembly to bepositioned on the upper surface of magnetic cover 308. Then, two screws374 are passed through holes 371 g and screwed into threaded holes 308 con the upper surface of magnetic cover 308. As a result, fixed screen109 together with structure body 302 is installed on magnetic cover 308.

FIG. 13A is a plan view illustrating a configuration around a peripheryof magnetic cover 308, before structure body 302 that supports fixedscreen 109 is installed on magnetic cover 308. FIG. 13B is a plan viewillustrating the configuration around the periphery of magnetic cover308, with structure body 302 that supports fixed screen 109 installed onmagnetic cover 308.

As illustrated in FIG. 13A, before structure body 302 is installed onmagnetic cover 308, beams 303 c of support member 303 are exposed, onthe positive side of the Z-axis, through cutouts 308 b of magnetic cover308. In contrast, after structure body 302 is installed on magneticcover 308, as illustrated in FIG. 13B, cutouts 308 b aligned in theX-axis direction are entirely covered by holder 371, and cutouts 308 baligned in the Y-axis direction are almost entirely covered by holder371. Holder 371 has widths in the X-axis direction and the Y-axisdirection that allow holder 371 to cover four cutouts 308 b as describedabove.

Cutouts 308 b are thus covered by holder 371, which prevents stray lightsuch as natural light travelling backward via the optical systemincluding mirror 22 from being condensed to, for example, beams 303 c ofsupport member 303. This can prevent beams 303 c and the like from beingheated to a high temperature and then damaged. Such light shieldingaction caused by holder 371 will be described later with reference toFIG. 16.

Next, an image display operation using movable screen 108 and fixedscreen 109 will be described.

FIG. 14A is a diagram schematically illustrating the positionalrelationship between movable screen 108 and fixed screen 109.

In the present exemplary embodiment, as described above, movable screen108 and fixed screen 109 are supported by holder 361 and holder 371,respectively. This configuration causes drive unit 300 to move onlymovable screen 108 in the optical axis direction (Z-axis direction). Forexample, in order to generate a depth image, movable screen 108 is movedwithin range W1 from position Ps0 to position Ps1. Fixed screen 109 isfixed at position Ps10. Herein, movable screen 108 and fixed screen 109are shifted from each other by distance D1 in the Z-axis direction.Fixed screen 109 is positioned closer to mirror 22 (optical system) thanmovable screen 108 is.

Note that a visual distance from driver 2 to the image (virtual image)becomes longer as movable screen 108 moves away from mirror 22illustrated in FIG. 1C. In other words, position Ps0 is a boundaryposition of movable screen 108 where the visual distance becomeslongest, and position Ps1 is a boundary position of movable screen 108where the visual distance becomes shortest. Fixed screen 109 ispositioned away from movable screen 108 in the positive direction of theZ-axis by distance D1, which causes an image (virtual image) displayedby fixed screen 109 to appear closer to driver 2 than an image (virtualimage) displayed by movable screen 108 is.

As described above, the present exemplary embodiment is configured tomove only movable screen 108, which allows movable screen 108 to bemoved only within range W1 necessary for a depth image to be displayed.This configuration allows movable screen 108 to be moved smoothly at ahigh speed.

FIG. 14B is a diagram schematically illustrating a scanning method oflaser light with respect to movable screen 108 and fixed screen 109.

In the image display operation, movable screen 108 is first scanned withthe laser beam. Movable screen 108 is sequentially scanned from scanline L1 set on the most positive side of the Y-axis to scan line Lk.During this scanning, holder 361 is moved toward the positive side ofthe Z-axis, which in turn moves movable screen 108 from position Ps0 toposition Ps1. This process causes the depth image to be displayed. Then,holder 361 is stopped. In this state, fixed screen 109 is sequentiallyscanned from scan line Lk+1 to scan line Lk. This process causes thefixed image to be displayed.

Note that, in the present exemplary embodiment, after the displayoperation of the fixed image is completed, an image whose visualdistance is not varied (hereafter, referred to as a “vertical image”) isdisplayed with movable screen 108 during a process in which movablescreen 108 is returned to position Ps0. The vertical image is an imagefor marking a pedestrian, for example, and is displayed so as to besuperimposed on the pedestrian at a position corresponding to a visualdistance of the pedestrian. In this process, movable screen 108 issequentially scanned from scan line Lk to scan line L1.

FIG. 15A is a graph illustrating an example of driving movable screen108 when an image illustrated in FIG. 15B is displayed in region S1.

Movable screen 108 is repeatedly moved with a period from time t0 totime t5 taken as one cycle. During a period from time t0 to time t1,movable screen 108 is moved from position Ps0 (farthest position) toposition Ps1 (nearest position), and during a period from time t2 totime t5, movable screen 108 is returned from position Ps1 (nearestposition) to position Ps0 (farthest position). During a period from timet1 to time t2, movable screen 108 is stopped at position Ps1 (nearestposition). A movement cycle of movable screen 108, that is, the periodfrom time t0 to time t5 is 1/60 seconds, for example. Movable screen 108is moved as illustrated in FIG. 15A by changing a current applied tocoil 341 described above while monitoring an output of the encoder ofposition detection unit 400.

In FIG. 15B, the period from time t0 to time t1 is a period fordisplaying depth image M1 extending in the depth direction, and theperiod from time t2 to time t5 is a period for displaying vertical imageM2 extending in the vertical direction. In FIG. 15B, the period fromtime t1 to time t2 is a period for displaying fixed image M3 in regionS2.

During the period from time t0 to time t1, laser light sources 101 a to101 c are caused to emit light at timing corresponding to depth image M1on scan lines corresponding to depth image M1 while movable screen 108is linearly moved from position Ps0 to position PS1, which causes depthimage M1 as illustrated in FIG. 15B to be displayed in region S1 as avirtual image.

Furthermore, movable screen 108 is stopped at position Ps1 during theperiod from time t1 to time t2. During this period, fixed screen 109 isscanned with the laser beam. Laser light sources 101 a to 101 c arecaused to emit light at timing corresponding to fixed image M3 on scanlines corresponding to fixed image M3, which causes fixed image M3 to bedisplayed in region S2 ahead of projection region 13.

Next, during the period from time t2 to time t5, movable screen 108 isreturned to position Ps0. At this time, movable screen 108 is stopped atposition Ps2 during a period from time t3 to time t4. During thisperiod, laser light sources 101 a to 101 c are caused to emit light attiming corresponding to vertical image M2 on scan lines corresponding tovertical image M2, which causes vertical image M2 as illustrated in FIG.15B to be displayed ahead of projection region 13 of windshield 12.

The above-described control is performed by image processing circuit 201illustrated in FIG. 2. Such control causes depth image M1 and verticalimage M2 to be displayed in region S1 as virtual images, and furthercauses fixed image M3 to be displayed in region S2 as a virtual image,during the period from time t0 to time t5. In the above-describedcontrol, respective display timings of depth image M1, vertical imageM2, and fixed image M3 are different from each other; however, thedifferences are extremely small, which allows driver 2 to recognize asuperimposed image including depth image M1, fixed image M3, andvertical image M2. Accordingly, driver 2 can view an image based on thevideo signal (depth image M1, vertical image M2, and fixed image M3)that has been superimposed on a scene including road R1 and pedestrianH1.

Note that, in the example of FIG. 15B, one vertical image M2 is present,and therefore one stop position (position Ps2) of movable screen 108 isset in the process of FIG. 15A. However, when a plurality of verticalimages M2 are present, a plurality of stop positions are set accordinglyin the process of FIG. 15A. Note that, in the process of FIG. 15A, theperiod from time t0 to time t5 is constant, and time t5 is unchanged.Therefore, the movement speed of movable screen 108 (slope of a waveformin FIG. 15A) before and after the stop positions is changed in responseto fluctuations in the number of stop positions.

Effects of Exemplary Embodiment

According to the above-described exemplary embodiment, the followingeffects are exerted.

The exemplary embodiment is configured to move only movable screen 108,which allows movable screen 108 to be moved only within a rangenecessary for a depth image to be displayed. This configuration allowsmovable screen 108 to be moved smoothly at a high speed.

Furthermore, structure body 302 (holder 371) that supports fixed screen109 covers an area around opening 308 a of magnetic cover 308 to blockstray light travelling backward via the optical system (mirror 22). Thisprevents an area around movable screen 108 from being irradiated withstray light of high intensity and then prevents the movable part(support member 303) located around movable screen 108 from being heatedto a high temperature by the stray light. Accordingly, the movable part(support member 303) located around movable screen 108 can be suitablyprotected from such stray light.

FIG. 16 is a diagram describing this effect. FIG. 16 is across-sectional view of structure body 302 taken along a plane parallelto the Y-Z plane. In FIG. 16, broken lines with arrows indicate straylight that has travelled backward via mirror 22 and condensed.

Stray light travelling toward support member 303 is blocked by magneticcover 308. Furthermore, stray light travelling toward cutouts 308 b ofmagnetic cover 308 is blocked by holder 371 of structure body 302. Asillustrated in FIG. 13B, ends of cutouts 308 b aligned in the Y-axisdirection are not covered by holder 371. However, as illustrated in FIG.16, stray light diagonally travels outward by the action of mirror 22(optical system). This prevents stray light from reaching support member303 through the ends of cutouts 308 b that are not covered by holder371. Accordingly, stray light travelling toward support member 303(beams 303 c) through cutouts 308 b are completely blocked by holder371. Therefore, the movable part (support member 303) located aroundmovable screen 108 can be suitably protected from stray light.

As described above, image display device 20 according to the presentexemplary embodiment is capable of moving movable screen 108 forgenerating a depth image smoothly at a high speed and suitablyprotecting the movable part located around movable screen 108 from straylight.

Note that stray light passing through opening 371 c of holder 371 andstray light passing through fixed screen 109 are both blocked by lightshielding member 363 of holder 361 that supports movable screen 108.Accordingly, the present exemplary embodiment can also prevent suchstray light from reaching support member 303.

Furthermore, the present exemplary embodiment has a configuration inwhich holder 371 has a light shielding property, and is adjusted inwidth so as to cover the area around opening 308 a of magnetic cover308. This eliminates the need for structure body 302 to include anylight shielding member that covers the area around opening 308 a otherthan holder 371. According to the present exemplary embodiment, theconfiguration can be simplified, and costs can be reduced.

Note that, in the present exemplary embodiment, holder 371 is irradiatedwith stray light, which may significantly increase the temperature ofholder 371. To address such a possibility, in the present exemplaryembodiment, as illustrated in FIG. 11B, installation areas for fixedscreen 109 (recesses 371 a illustrated in FIG. 11A) are shielded bylight shielding members 372, which prevents the temperature of theinstallation areas (recesses 371 a illustrated in FIG. 11A) with whichfixed screen 109 directly comes into contact from being significantlyincreased. This can prevent fixed screen 109 from being damaged by anincrease in the temperature of the installation areas (recesses 371 aillustrated in FIG. 11A) caused by stray light.

Furthermore, in the present exemplary embodiment, the gap is formed inthe Z-axis direction between light shielding members 372 and the ends offixed screen 109. Thus, even when light shielding members 372 areincreased in temperature by irradiation with stray light, heat generatedin light shielding members 372 is prevented from directly transmittingto fixed screen 109. Accordingly, fixed screen 109 can be prevented frombeing damaged by the increase in the temperature of light shieldingmembers 372 caused by stray light.

Furthermore, in the present exemplary embodiment, as illustrated in FIG.12B, gap G2 is formed between fixed screen 109 and a portion of holder371 on the positive side of the Y-axis. Thus, even when the portion ofholder 371 on the positive side of the Y-axis is increased intemperature by irradiation with stray light, heat generated in theportion is prevented from directly transmitting to fixed screen 109.Accordingly, fixed screen 109 can be prevented from being damaged by theincrease in the temperature of holder 371 caused by stray light.

Furthermore, in the present exemplary embodiment, structure body 302 isinstalled on magnetic cover 308, which allows structure body 302 to behoused compactly and allows the positional relationship between movablescreen 108 and fixed screen 109 to be suitably maintained.

Furthermore, in the present exemplary embodiment, drive unit 300includes coil 341 installed on the movable part (support member 303),and magnetic circuit 307 that applies a magnetic field to coil 341,which allows movable screen 108 to be moved smoothly at a high speed.Furthermore, magnetic cover 308 is made of a magnetic material, andcovers magnetic circuit 307 to function as a yoke of magnetic circuit307, which makes it possible to reduce a number of components and toshield the movable part (support member 303) from stray light.

Furthermore, in the present exemplary embodiment, as illustrated in FIG.10A, heat resistant packing 362 is interposed between movable screen 108and light shielding member 363. Thus, even when light shielding member363 is increased in temperature by irradiation with stray light, heatgenerated in light shielding member 363 is prevented from directlytransmitting to movable screen 108. Accordingly, movable screen 108 canbe prevented from being damaged by the increase in the temperature oflight shielding member 363 caused by stray light.

Furthermore, in the present exemplary embodiment, as illustrated in FIG.10A and FIG. 10B, stepped part 361 a is shielded by light shieldingmember 363, which prevents stepped part 361 a from being heated to ahigh temperature by stray light. Accordingly, movable screen 108 can beprevented from being damaged by heat from stepped part 361 a.

Modification Example

Although the exemplary embodiment of the present disclosure has beendescribed above, the present disclosure is not limited to the exemplaryembodiment described above, and moreover, a variety of modifications canbe applied to application examples according to the present disclosurebesides the exemplary embodiment described above.

For example, in the exemplary embodiment, structure body 302 isinstalled on magnetic cover 308. Alternatively, structure body 302 maybe installed on support base 306 or fixing base 310. Note that, as inthe exemplary embodiment, the configuration in which structure body 302is installed on magnetic cover 308 allows structure body 302 to behoused more compactly.

Furthermore, in the exemplary embodiment, as illustrated in FIG. 13B,the ends of cutouts 308 b aligned in the Y-axis direction are notcovered by holder 371. In a case where stray light enters through theends due to the action of the optical system (mirror 22), holder 371 maybe increased in width in the Y-axis direction so as to entirely covercutouts 308 b aligned in the Y-axis direction. The widths of holder 371in the X-axis direction and the Y-axis direction may be appropriatelyadjusted in order to shield the movable part from stray light.

Furthermore, in the exemplary embodiment, the movable part (supportmember 303, structure body 301) is shielded from stray light by holder371. Alternatively, a separate light shielding member may be installedon holder 371 so that both the light shielding member and holder 371blocks stray light. However, this configuration increases both thenumber of components and a workload required for assembly as compared tothe exemplary embodiment.

Furthermore, in the exemplary embodiment, movable screen 108 and fixedscreen 109 are installed to be sloped with respect to a planeperpendicular to the Z-axis; however, both or either of movable screen108 and fixed screen 109 may be installed to be perpendicular to theZ-axis. Slope angles of movable screen 108 and fixed screen 109 can beappropriately adjusted. Furthermore, shapes and sizes of movable screen108 and fixed screen 109 are also not limited to those described in theexemplary embodiment.

Furthermore, in the exemplary embodiment, an example has been given inwhich the present disclosure is applied to the head-up display mountedon passenger vehicle 1; however, the present disclosure is not limitedto such an on-vehicle application, but is also applicable to other typesof image display devices.

Moreover, the configurations of image display device 20 and irradiationlight generator 21 are not limited to the configurations illustrated inFIG. 1C and FIG. 2, and can be modified as appropriate. Furthermore, theconfiguration of drive unit 300 that moves movable screen 108 is notlimited to the configuration described in the exemplary embodiment andcan be modified as appropriate. For example, a configuration in which adrive unit of a piezoelectric type or an electrostatic type drivesmovable screen 108 may be employed.

The exemplary embodiment of the present disclosure can be modified invarious ways as appropriate within the scope of the technical ideadisclosed in the claims.

The image display device according to the present disclosure is capableof moving a screen for generating a depth image smoothly at a high speedand suitably protecting the movable part located around the screen fromstray light. Therefore, the present disclosure is industrially useful.

What is claimed is:
 1. An image display device comprising: a lightsource; a movable screen that is irradiated with light from the lightsource to form an image; a fixed screen that is irradiated with thelight from the light source to form an image; a scanning unit that usesthe light from the light source to scan the movable screen and the fixedscreen; an optical system that uses light from the movable screen andlight from the fixed screen to generate a virtual image; a drive unitthat moves the movable screen in an incident direction of the lightincident from the light source on the movable screen; a fixed supportpart that supports the fixed screen at a fixed position such that thefixed screen is closer to the optical system than the movable screen is;and a cover that covers the drive unit, wherein the cover has an openingthat guides the light from the scanning unit to the movable screen andthe light from the scanning unit to the fixed screen, the drive unit isconfigured to support the movable screen so as to allow the movablescreen to protrude toward the optical system through the opening, andthe fixed support part is configured to cover an area of the coveraround the opening to shield a movable part of the drive unit from straylight travelling backward via the optical system.
 2. The image displaydevice according to claim 1, wherein the fixed support part includes aholder that has a light shielding property and supports the fixedscreen, and the holder is configured to cover the area around theopening.
 3. The image display device according to claim 2, wherein thefixed support part includes a light shielding member that shields theholder from the stray light at an installation position of the fixedscreen.
 4. The image display device according to claim 3, wherein thelight shielding member is installed on the holder such that a gap isformed between the light shielding member and the fixed screen.
 5. Theimage display device according to claim 1, wherein the fixed supportpart is installed on the cover.
 6. The image display device according toclaim 1, wherein the cover includes a cutout that extends outward fromthe opening and through which a support member that supports the movablescreen is partially inserted, and the fixed support part is configuredto cover the cutout.
 7. The image display device according to claim 1,wherein the drive unit includes: a coil that is installed on the movablepart; and a magnetic circuit that applies a magnetic field to the coil,and the cover is made of a magnetic material, and covers the magneticcircuit to function as a yoke of the magnetic circuit.